It is known that the embossing units are commonly used in the paper converting plants to produce, for example, rolls of kitchen paper, toilet paper, paper towels and so on. The embossing has the main function to confer greater volume, higher liquid absorption capacity and surface designs to the plies that form the paper web which is subsequently rolled on cardboard tubes by means of a rewinder and then subjected to transverse cut in cutting-off machines.
Essentially, the embossing process implies the passage of one or more plies of paper between an embossing roller, the surface of which is provided with tips or reliefs according to a predefined scheme, and a counter-roller. Therefore, a ply that is smooth before the embossing process takes place, is so shaped as to exhibit a set of reliefs and depressions corresponding to the arranged embossing pattern on the embossing roller. If the web is composed by more plies, for example two, these can be both embossed and then joined together by gluing in a so-called tip-to-tip configuration, in which the reliefs of a ply are opposite to the other's ply reliefs, or in so-called nested configuration in which the reliefs of a ply are in each other's ply depressions.
The machines in which the embossing process takes place are commonly called “embossing units”. Generally, the embossing units are arranged to allow the rollers exchange, i.e. the replacement of one or more embossing rollers to change the embossing patterns on the paper or for maintenance operations. Generally, such embossing units have a structure comprising a fixed part and a movable part which is moved with respect to the fixed part to allow access to the parts supporting the embossing rollers in order to release and replace the latter when required. U.S. Pat. No. 7,618,004, EP1765584 and U.S. Pat. No. 7,458,538 disclose embossing units of this type.
The embossing rollers for use in machines of the type described above are stored in special areas of the plant and are shaped specifically to be picked up and moved by suitable handling systems arranged in the paper converting plant.